Running the back office of a UK online retailer

The client

A fast-growing UK online retailer selling across Amazon, eBay, Shopify, TikTok Shop and its own website.

The challenge

Selling on a dozen marketplaces from its own warehouses means thousands of prices, orders, parcels and stock levels changing every day. Off-the-shelf tools covered parts of the job, but none of them joined buying, the warehouse, pricing and the money together in the way this business works.

What we built

The system the whole business runs on, used every day by buyers, warehouse staff, customer service, finance and managers. The main areas each have their own in-depth case study below; this is the tour.

Orders

• Orders from every marketplace in one list, with the full history of each: items, profit, notes, events, returns and payments
• Orders split automatically by stock location, with pre-order items held back until their release date
• Dispatch deadlines and each courier's daily allowance worked out automatically, on a calendar the team can adjust
• VAT invoices on demand, and bulk tools for fixing or recalculating orders

Customer service and returns

• A shared diary of tasks and alerts, so nothing that needs a person is missed
• Returns, refunds and exchanges recorded against the order, with reasons, a refund calculator and replacement orders
• Claims against couriers and marketplaces, with proof-of-delivery documents and responses uploaded in bulk
• Returns raised on Amazon and Shopify imported automatically, and returned parcels scanned in at the warehouse
• Dispatch and delay emails to customers, and a log of who has viewed each customer's personal details

The warehouse

• Staff log in by scanning their badge, and every scan is logged
• A map of each building that managers can redraw themselves, with routes planned for every pick list
• Deliveries booked in, checked on arrival and put away where the system suggests
• Stock moved between buildings by lorry, and stock counts done on a phone
• Picking, packing and dispatch screens, label printers and leaderboards on the warehouse TVs

Buying and suppliers

• Supplier price lists turned into purchase orders, with the true cost once duty and shipping are added
• A range planner and buying desk with sales history and profit beside every decision
• A secure supplier portal for orders sent direct to customers, stock updates and returns
• Weekly reports and stock alerts emailed to suppliers automatically

Products, listings and prices

• A product catalogue with brands, licences, seasons and kits, and photos taken as stock arrives
• Listings on 12 Amazon marketplaces, Shopify, TikTok Shop and eBay, created and kept in step from one place
• Repricing from a single grid or a spreadsheet, with alerts the moment a competitor changes price
• Slow sellers spotted automatically and moved through planned price drops to clearance

Money

• The true profit on every item sold, corrected automatically as the real figures arrive
• Marketplace settlements and payment-provider payouts matched against what was expected
• VAT rates per item, import duty, and the cost of storage in Amazon's warehouses and the retailer's own
• A profit dashboard and weekly trading report used from the warehouse floor to the board

Staff and security

Rights by group and by person, two-factor sign-in, trusted networks, automatic archiving of unused accounts, and break schedules for warehouse shifts.

Keeping itself healthy

Around 170 scheduled jobs keep the system in step with the marketplaces, payment providers and the order hub around the clock. Built-in checks look for inconsistent data, health and speed pages show how the system is performing, and staff report problems from inside the system, with a screenshot, straight onto the development team's board.

Channels come and go

Over thirteen years the retailer has started and stopped selling on several marketplaces, moved its own web shop from one platform to another, and changed payment providers and accounting software. Each time, the system moved with it, and the old connections were retired cleanly.

Moving to modern technology, without stopping

In 2026 we built the tools to convert the whole system to modern technology automatically, and to check, page by page, that nothing changes for the people using it. Staff now use the converted system alongside the original, and the business has carried on trading throughout.

Working together

We work alongside the retailer's own team. Since 2026 an AI agent has worked as part of that team, researching, planning and making changes that a developer approves before anything goes live.

Technical details

About 30 projects and half a million lines, built on .NET with SQL Server (300+ tables, the largest holding over 100 million rows), plus a background service of about 170 scheduled tasks. Separate client libraries for the Amazon Selling Partner API, Shopify Admin GraphQL, TikTok Shop and eBay; Linnworks through our own API client.

Converted from VB.NET to C# in 2026 by our own tooling, with compiled-output comparison and page-by-page screenshots. Over 2,800 automated tests and CI on every pull request.

• C#
• VB.NET
• .NET
• ASP.NET MVC
• SQL Server
• Entity Framework
• Azure Cosmos DB
• AWS
• Azure DevOps